1. Field of the Invention
The present invention relates to ammunition handling systems and particularly to an improved drive system for powering ammunition magazine conveyors.
2. Description of the Related Prior Art
Ammunition magazines serving rapid-fire guns typically include a conveyor for circulating rounds of ammunition throughout the magazine interior enroute to an outlet port from which the ammunition rounds are serially delivered to the gun for firing. The magazine conveyor is typically in the form of an endless chain conveyor trained around a plurality of distributed, turnaround sprocket sets in a serpentine path to maximize magazine storage capacity. The ammunition rounds are confined in a succession of carriers connected to the chain conveyor at regular intervals. Propulsion of the magazine conveyor often requires that the conveyor drive system distribute power to plural turnaround sprocket sets located at appropriate intervals along the conveyor run between one or more idler turnaround sprocket sets. For high capacity ammunition magazines, the spacings between driven sprocket sets can be large.
In the case of large caliber ammunition magazines, the ammunition feed rate is relatively low, and thus the sprocket sets may rotate at rather low speeds of, for example, 1 to 10 rpm. However, high performance conveyor prime movers typically operate at substantially higher speeds of, for example, 2000 to 6000 rpm. Consequently, a very large speed reduction must be introduced into the conveyor drive system between the prime mover or motor and the driven sprocket sets.
A typical practice is to introduce the requisite large speed reduction immediately at the output of the conveyor prime mover. Consequently, the power is distributed to the driven sprocket sets from the output of the speed reducer, typically a high reduction gear box, at a relatively slow speed with accompanying high torque. To handle this torque, the drive train components must be physically robust, thus adding size, weight and cost to the magazine design.
An alternative approach is to distribute power to the drive sprocket sets at high speed and low torque, and then introduce the requisite speed reductions at the sites of each of the driven sprocket sets. This approach typically involves implementation of drive trains including separate spur gear reduction boxes drivingly connected to each of the driven sprockets, which, in turn, are driven off the prime mover via interconnecting chains or belts. Such drive trains are difficult to package in an efficient ammunition magazine design and represent a significant expense.